This application is the national phase under 35 U.S.C. xc2xa7371 of PCT International Application No. PCT/JP99/00147 which has an International filing date of Jan. 18, 1999 which designated the United States of America.
The present invention relates to a chlorinated organic compound collector and, particularly, to a collector for collecting chlorinated organic compounds contained in a fluid.
Chlorinated organic compounds such as dioxins, polychlorobiphenyl (PCB), chlorophenol and chlorobenzene are generally contained in exhaust gas emitted from incineration plants for incineration of waste such as industrial waste and domestic refuse.
The term xe2x80x9cdioxinsxe2x80x9d is herein a generic term for polychlorinated dibenzo-para-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and the like, which are well known as highly toxic environmental pollutants. Among these, tetrachlorodibenzodioxins (T4CDDs) are known to be the most toxic. On the other hand, chlorinated organic compounds such as polychlorobiphenyl, chlorophenol and chlorobenzene are less toxic than dioxins. However, it has been found that these chlorinated organic compounds are liable to be converted into dioxins in a temperature range of the exhaust gas under certain conditions in an incinerator, for example, with various elements in flyash serving as a catalyst, so that these chlorinated organic compounds are recognized as environmental pollutants like dioxins. From the viewpoint of environmental preservation, it is imperative to establish a method of removing the aforesaid various chlorinated organic compounds from a fluid such as exhaust gas or waste water and, at the same time, efforts are being made urgently on a worldwide scale to establish a method of analyzing the chlorinated organic compounds contained in the fluid.
When the chlorinated organic compounds present in the fluid are to be analyzed, it is necessary to first obtain a sample from the target fluid in a precise and accurate manner. For the analysis of the chlorinated organic compounds present in an exhaust gas, for example, it is necessary to take a predetermined amount of a gas sample from a space such as a flue through which the exhaust gas is flowing, and assuredly capture the entire amount of the various chlorinated organic compounds contained in the gas sample. In particular, the aforesaid dioxins as the environmental pollutants are contained in a very small amount in the gas sample, and include various kinds of dioxins which are present in various forms such as particulate and gaseous forms. Therefore, a highly reliable result cannot be expected from the analysis without precise sampling. For this reason, Japan, the United States and European countries have been making attempts to formulate official guidelines for methods of taking a sample containing chlorinated organic compounds such as dioxins to ensure the accuracy of the result of the analysis.
In Japan, for example, the Ministry of Health and Welfare has formulated an official guideline, which specifies a sampling device for taking a gas sample containing chlorinated organic compounds such as dioxins. The sampling device principally comprises: a sampling tube for taking a gas sample, for example, from a flue through which an exhaust gas from an incinerator flows; a first captor including a filtering material for mainly capturing a particulate component of the chlorinated organic compounds contained in the gas sample taken through the sampling tube; and a second captor for capturing a gaseous component of the chlorinated organic compounds uncaptured by the first captor. The second captor principally comprises a liquid captor portion including a plurality of glass impingers each retaining therein an absorbent liquid, and a resin adsorbent portion including a resin adsorbent, whereby the gaseous component of the chlorinated organic compounds uncaptured by the first captor is captured by the absorbent liquid in the impingers and the resin adsorbent.
In most cases, the sampling device is repeatedly used, because the device is expensive with a complicated construction including the first captor and the second captor and with many glass components incorporated therein. Since the components, such as the impingers, of the sampling device should be kept clean to ensure the reliability of measurement data, preparatory operations such as a cleaning operation to be performed prior to the gas sampling are very troublesome. In addition, when the gaseous component of the chlorinated organic compounds contained in the gas sample is captured by the second captor, the second captor should be cooled by a coolant such as dry ice. Therefore, a sampling operation per se is very troublesome. Further, the chlorinated organic compounds captured by the first captor and the second captor are extracted after the gas sampling. At this time, the respective components of the chlorinated organic compounds captured by the first captor and the second captor should separately be extracted. This makes the extracting operation troublesome. In addition, the technique of the extracting operation often influences the reliability of the result of the analysis. Moreover, the sampling device has difficulties in handing at the gas sampling and transportation, because the sampling device inevitably has a larger size with the two kinds of captors, i.e., the first captor and the second captor, and is vulnerable to damage with many glass components.
On the other hand, the U.S. Environmental Protection Agency (EPA) and the Comite Europeen de Normalisation (CEN) have also formulated their own official guidelines. Sampling devices specified in these guidelines have substantially the same drawbacks in the complexity of the device construction and the handling difficulty with some minor differences from the sampling device specified in the Japanese guideline.
It is an object of the present invention to simultaneously capture particulate and gaseous chlorinated organic compounds contained in a fluid for collection thereof.
A chlorinated organic compound collector according to the present invention is intended for collecting chlorinated organic compounds contained in a fluid. The collector comprises: a vessel which permits passage of a fluid therethrough; and a captor disposed within the vessel for simultaneously capturing particulate and gaseous chlorinated organic compounds contained in the fluid for removal thereof from the fluid. The captor includes, for example, an adsorbent capable of adsorbing the chlorinated organic compounds.
In accordance with a first embodiment, the captor for use in the collector includes, for example, a gas-permeable tube having a closed end, and a gas-permeable sheet fitted around the gas-permeable tube, wherein the gas-permeable sheet includes an adsorbent capable of adsorbing the chlorinated organic compounds. The gas-permeable tube is, for example, a porous tube. The gas-permeable sheet is, for example, a paper-like sheet comprising the adsorbent and inorganic fibers, and may be in a felt form or in a laminate form.
In accordance with a second embodiment, the captor for use in the collector is, for example, a hollow cylindrical member which is formed from a gas-permeable paper-like sheet comprising inorganic fibers and an adsorbent capable of adsorbing the chlorinated organic compounds and has a closed end. In accordance with a third embodiment, the captor is, for example, a gas-permeable hollow cylindrical molded member which comprises inorganic fibers and an adsorbent capable of adsorbing the chlorinated organic compounds and has a closed end.
The adsorbent for use in the collector of the invention is, for example, an activated carbon. The activated carbon is, for example, at least one of a granular activated carbon and a fibrous activated carbon. The activated carbon has a specific surface area of 50 to 4,000 m2/g, for example. In this case, the activated carbon is present, for example, in an amount of 0.1 to 4.0 g in the captor.
When the chlorinated organic compounds contained in the fluid are to be collected with the use of the chlorinated organic compound collector according to the present invention, the fluid is allowed to pass through the vessel. At this time, the fluid passes through the captor disposed within the vessel, and the particulate and gaseous chlorinated organic compounds contained in the fluid are simultaneously captured by the captor for removal thereof. As a result, the particulate and gaseous chlorinated organic compounds in the fluid are collected by the captor.
With the captor according to the first embodiment, the fluid flowing into the vessel passes through the captor, and is then discharged out of the vessel. At this time, the fluid passes through the gas-permeable tube and gas-permeable sheet of the captor in this order, whereby the particulate and gaseous chlorinated organic compounds are removed by the gas-permeable tube and the adsorbent contained in the gas-permeable sheet. That is, the particulate and gaseous chlorinated organic compounds are collected and removed from the fluid by the captor.
With the captor according to the second embodiment, the fluid flowing in to the vessel passes from the inside to the outside of the gas-permeable paper-like sheet of the captor, and is then discharged out of the vessel. At this time, the particulate and gaseous chlorinated organic compounds contained in the fluid are removed by the inorganic fibers and the adsorbent constituting the gas-permeable paper-like sheet. That is, the particulate and gaseous chlorinated organic compounds are collected and removed from the fluid by the captor.
With the captor according to the third embodiment, the fluid flowing into the vessel passes from the inside to the outside of the hollow cylindrical molded member of the captor, and is then discharged out of the vessel. At this time, the particulate and gaseous chlorinated organic compounds contained in the fluid are removed by the inorganic fibers and the adsorbent constituting the hollow cylindrical molded member. That is, the particulate and gaseous chlorinated organic compounds are collected and removed from the fluid by the captor.
Where the adsorbent for use in the captor is an activated carbon, the chlorinated organic compounds can assuredly be captured and removed from the fluid by the activated carbon, which has a particularly excellent adsorption property with respect to the chlorinated organic compounds. Where the activated carbon has a specific surface area of the aforesaid range, the activated carbon exhibits a further excellent adsorption property with respect to the gaseous chlorinated organic compounds, so that the chlorinated organic compounds in the fluid can further assuredly be captured and removed from the fluid. In this case, where the activated carbon is contained in an amount of the aforesaid range in the captor, the chlorinated organic compounds collected by the captor can easily be extracted in a short time in accordance with an inexpensive and simple extraction method with a general versatility by using a high speed extractor or a Soxhlet extractor.
Since the chlorinated organic compound collector according to the present invention includes the captor which is capable of simultaneously capturing the particulate and gaseous chlorinated organic compounds, the collector has a simpler construction and is easier to handle than the conventional collector. Therefore, the chlorinated organic compounds contained in the fluid can quickly, easily and assuredly be collected with the use of the collector. In addition, the extracting operation for extracting the chlorinated organic compounds collected by the collector is remarkably simplified as compared with a case where the conventional collector is used.
On the other hand, a chlorinated organic compound sampling method according to the present invention is intended for collecting chlorinated organic compounds contained in a fluid. The method comprises the step of simultaneously capturing particulate and gaseous chlorinated organic compounds contained in the fluid for removal thereof from the fluid.
Since the sampling method merely includes the step of simultaneously capturing the particulate and gaseous chlorinated organic compounds contained in the fluid for removal thereof from the fluid, a sampling operation for collecting the chlorinated organic compounds can be simplified as compared with the conventional method in which the particulate and gaseous components of the chlorinated organic compounds are separately collected. As a result, the sampling operation can easily be performed.
Other objects and effects of the present invention will become apparent from the following detailed description.